The present invention relates generally to transport conveyors for conveyance of bulk materials such as coal, rock, pulpwood logs, and the like, and more particularly to an improved idler roller for a bulk conveyor which includes stub shafts for enhancing the service life of the associated bearings of the idler roller.
Belt conveyors are widely used for transport of bulk materials such as coal, rock, pulpwood logs, and the like, frequently in an outdoor environment. These types of conveyors have attained such widespread use by virtue of their inherent economy, reliability, and versatility. In addition, they are suitable for performing numerous processing functions in connection with their normal purpose of providing a continuous flow of material between operations. More recently, the conformity of belt conveyors to environmental requirements has further enhanced their desirability over alternative means of transport. Low labor and low energy requirements further enhance their versatile and economical use.
For transport of bulk materials, belt conveyors are typically configured to include an upper run along which materials are carried by forming the belt of the conveyor into a trough shape. To this end, a conveyor system includes groups of so-called troughing idler rollers, typically mounted in groups of three, with a pair of upwardly angled idler rollers positioned on opposite sides of a central, generally horizontal idler roller. This configuration of the idler rollers permits the associated belt to assume a trough shape under the weight of bulk materials being transported, with the belt thus being guided and supported by each group of idler rollers.
In typical constructions, the troughing idler rollers of a belt conveyor employ either ball bearings or tapered roller bearings supported by a through shaft or axle inside the idler roll. The shaft is typically stationary, and the bearings allow the roll body and surface (or shell) to rotate about the shaft, thus giving support to the moving conveyor belt with minimum frictional losses. Typically, two bearing assemblies are provided for each roll, one at each end of the roll for mounting on the associated through shaft.
As will be appreciated, the service life of the bearings of an idler roller are critical to the roller""s useful life. In this regard, bearing misalignment, caused by shaft deflection resulting from service loading, is one of the principal factors affecting bearing service. In calculating bearing life, the normal service life of a bearing is normally reduced in accordance with expected shaft misalignment resulting from loading.
The present invention is directed to an improved idler roller construction for transport conveyors which includes an arrangement of stub shafts and tapered roller bearings which are configured to minimize shaft deflection and resultant misalignment, thus desirably enhancing the expected service life of the bearings, thereby enhancing the service life of the idler roller assembly.
An idler roller for a transport conveyor embodying the principles of the present invention includes a cylindrical roller shell having opposite open ends, and a pair of roller heads respectively fitted to the opposite ends of the roller shell. A pair of bearing assemblies are respectively fitted to the pair of roller heads, with a pair of stub shafts respectively fitted in each of the bearing assemblies. The stub shaft idler roller design provides an overall geometry, including the specific locations of the shaft and bearings relative to each other, that desirably acts to minimize the amount of shaft slope or deflection, for a given load, through the bearings, thus extending the service life of the bearings.
In accordance with the illustrated embodiment, each of the bearing assemblies of the idler roller comprises a pair of roller bearings, more specifically, a pair of indirect mounted tapered roller bearings. While tapered roller bearings are particularly sensitive to shaft misalignment, minimization of such misalignment provided by the present invention desirably enhances the service life of the tapered roller bearings.
Further features of the present idler roller construction enhance its reliable operation. The idler roller includes a pair of oil seals each of which extend between a respective one of the stub shafts and the associated roller heads, outboard of the respective one of the bearing assemblies. Each oil seal comprises an outer elastomeric element, typically urethane, having at least one peripheral seal lip for sealing engagement with the respective one of the roller heads. The oil seal further includes an inner element juxtaposed to the outer element to form a labyrinth seal therewith.
In the illustrated embodiment, each roller head of the idler roller comprises a circular end cap portion, and an outer support surface extending inwardly from the end cap portion within a respective open end of the roller shell. Each roller head further includes an inner bearing cavity extending inwardly from the end cap portion within which the respective one of the bearing assemblies is fitted. In accordance with the illustrated embodiment, each of the roller heads includes a plurality of radially oriented reinforcing webs extending between the outer support surface and the inner bearing cavity. The idler roller is thus straightforward and robust in construction, again desirably enhancing reliable operation and long service life.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.